Microwave structure measurements on the cyclopropane–HCN complex

Abstract

Microwave rotational transitions for the cyclopropane-HCN complex were observed using the Flygare–Balle pulsed beam Fourier transform spectrometer. The 111→212, 101→202, 110→211, 212→313, 202→303, 211→312, 313→414, 303→404, 312→413, 414→515, 404→505, and 413→514 transitions were observed. The rotational constants obtained are A=20 243±1344 MHz, B=1384.209±0.001 MHz, and C=1327.901±0.001 MHz. The distortion constants are DJ=1.53±0.03 kHz and DJK=50.9±1.1 kHz. The nitrogen quadrupole coupling strength is eQqaa=−4.38±0.01 MHz with eQqbb−eQqcc= 0.002±0.003 MHz. The cyclopropane carbon atoms and HCN lie in a plane. The most reasonable bond distance is obtained with the HCN hydrogen atom bonding to the midpoint between two of the cyclopropane carbon atoms. The separation of the centers of mass of HCN and cyclopropane is Rcm= 4.472±0.002 Å. The HCN carbon atom is RCC–C=3.476±0.002 Å from the cyclopropane carbon–carbon bond. The stretching force constant is ks=0.062 mdyn/Å and the approximate bonding energy is 860 cm−1.